The present invention relates to a fluidized bed discharge bin wherein the bin is aerated to fluidize the contents contained therein and increase the ease with which the contents may be discharged. More particularly, the present invention is a fluidizing closure for covering a hopper opening in the bottom of the bin.
Bulk material such as particulates and powders are often transported in large bins. However, before the materials may be put to use, it is necessary to discharge the materials from the bin. Various techniques and apparatuses are presently used for emptying these bins. One such technique involves the introduction of air into the bin to fluidize the particulates or powdered materials. Once fluidized, the contents readily flow from the bin during discharge.
While fluidization has made the discharging of bins easier, problems remain in that these bins require large discharge openings and that, when closed, the openings are susceptible to leakage. U.S. Pat. No. 4,439,072, issued Mar. 27, 1984, discloses a discharge system incorporating a fluidizing closure that enables the contents of a bin to be discharged through a comparatively small opening that is easily sealed. The present invention is an advancement on the above mentioned patent which is hereby incorporated by reference.
Another problem associated with some of the prior art fluidization bins is "rat holing". Rat holing involves the situation where an air path develops through the particulated material from the source of the aeration up through the bin contents. Once established, the rat hole relieves the pressure of the air and precludes the proper fluidization formation.
One way of fluidizing particulates in a bin and avoiding rat holing is to introduce the aeration to one side of an air-permeable material, such as a fabric sheet, on which the particulates are disposed. The air circulates beneath the fabric and then permeates up through the fabric and fluidizes the particulates in a substantially even manner. Such a device was first disclosed in the '072 patent mentioned previously.
The present invention is directed to an improved spout or closure for fluidizing the contents of a discharge bin. While incorporating all of the advancements of the prior art, including discharge through an easily sealed opening and the avoidance of rat holing, the present invention discloses a construction which employes simplified fabrication techniques, increases storage capacity, improves fluidization, and enhances operator accessibility.
It is therefore an object of the present invention to provide a closure cap having a construction which utilizes simplified fabrication techniques.
It is a further object of the present invention to provide a closure cap which allows the bin to store and handle an increased amount of bulk material without a corresponding increase in the overall size of the bin.
The present invention also has as one of its objects the improvement of air flow during fluidization and therefore an increased discharge rate for the contents of the bin.
Still another object of the invention is to increase operator accessibility to the discharge outlet of the closure.
In summary, the present invention incorporates a square based closure for attachment to an opening in the lower hopper of a storage bin. The sides of the closure converge in a downwardly extending direction so as to form a generally pyramidal shape. The convergence angle of each wall is varied such that the convergence point of all four walls is offset from the central axis of the bin. A discharge outlet is positioned adjacent to the convergence point on the wall having the smallest convergence angle. A sheet of air-permeable material, corresponding in shape to that of the closure and containing apertures aligning with the discharge outlet and the hopper opening, forms a lining on the interior of the closure. A spacer is positioned between the air-permeable material and the interior surfaces of the closure and extends along the midsection of the interior walls of the closure to create and air space therebetween. The closure also includes an air inlet at approximately the same height as the spacer. During operation, air enters through the air inlet, penetrates the air-permeable material and fluidizes the contents of the bin for discharge.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.